Cut broccoli in small florets and place them in the medium-sized bowl.
Cube beets in 2-inch chunks (they don’t have to be uniform) and place the chunks in the same bowl with florets.
Roughly chop up garlic cloves and add to the bowl along with 1 TBSP of lemon juice.
Slice medium onion into 1/4 of inch strips and add to the bowl.
Add oil, salt, and pepper in the bowl.
Mix all the ingredients well. Place the vegetables on the baking sheet and spread them out.
Turn the oven on and heat it to 400F.
Positioning it in the middle rack, place the baking sheet into the well-heated oven for 15 minutes. Once the time is up, take the baking sheet out, mix the vegetables making sure all of them are getting even cooking and place it back into the oven for another 10 minutes.
Once the time is up, your beautiful masterpiece is ready to be consumed. If you wish to adjust the seasoning do so at this point.